Implicit channel tracking for simultaneous multiuser transmission

ABSTRACT

Embodiments of the present disclosure provide for implicit channel tracking for simultaneous multiuser transmissions. Other embodiments may be described and claimed.

FIELD

Embodiments of the present invention relate generally to the technicalfield of wireless communications.

BACKGROUND

The Institute of Electrical and Electronics Engineers (IEEE) 802.11standards are expected to support efficient transmission for multiuser(MU) and a single user (SU) beamforming transmutations to transmit to alarge number of stations with different link conditions and quality ofservice (QoS) characteristics.

Multiuser—multiple input multiple output (MU-MIMO) needs a preciseestimate of a channel from an access point transmitter to a user'sreceiver. See, for example, IEEE 802.11 ac-2013-IEEE Standard forInformation technology—Telecommunications and information exchangebetween systems—Local and metropolitan area networks—Specificrequirements—Part 11: Wireless LAN Medium Access Control (MAC) andPhysical Layer (PHY) Specifications—Amendment 4: Enhancements for VeryHigh Throughput for Operation in Bands below 6 GHz (hereinafter, “IEEE802.11ac”). This estimate of the channel is needed for the transmitterto select weight factors that reduce mutual interference among differentuser streams. Currently, channel knowledge is acquired explicitly fromthe user's receivers. This channel acquisition process has highthroughput overhead. Further, the channel can change after a shortperiod of time, which may increase mutual interference between users anddeteriorate user reception.

To overcome channel change problems, some systems will have atransmitter explicitly acquire a wireless channel more frequently.However, these systems will increase the associated high overhead ofchannel acquisition and, therefore, compromise system efficiencies.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments will be readily understood by the following detaileddescription in conjunction with the accompanying drawings. To facilitatethis description, like reference numerals designate like structuralelements. Embodiments are illustrated by way of example and not by wayof limitation in the figures of the accompanying drawings.

FIG. 1 illustrates a network in accordance with some embodiments.

FIG. 2 illustrates a transmission diagram in accordance with someembodiments.

FIGS. 3A-3B illustrate high-efficiency packets in accordance with someembodiments.

FIG. 4 illustrates signal processing circuitry in accordance with someembodiments.

FIG. 5 illustrates an operation flow/algorithmic structure in accordancewith some embodiments.

FIG. 6 illustrates an operation flow/algorithmic structure in accordancewith some embodiments.

FIG. 7 illustrates an operation flow/algorithmic structure in accordancewith some embodiments.

FIG. 8 illustrates an example device in accordance with variousembodiments.

FIG. 9 is a block diagram illustrating components, according to someexample embodiments, able to read instructions from a machine-readableor computer-readable medium (for example, a non-transitorymachine-readable storage medium) and perform any one or more of themethodologies discussed herein.

DETAILED DESCRIPTION

The following detailed description refers to the accompanying drawings.The same reference numbers may be used in different drawings to identifythe same or similar elements. In the following description, for purposesof explanation and not limitation, specific details are set forth suchas particular structures, architectures, interfaces, techniques, etc. inorder to provide a thorough understanding of the various aspects ofvarious embodiments. However, it will be apparent to those skilled inthe art having the benefit of the present disclosure that the variousaspects of the various embodiments may be practiced in other examplesthat depart from these specific details.

In certain instances, descriptions of well-known devices, circuits, andmethods are omitted so as not to obscure the description of the variousembodiments with unnecessary detail. For the purposes of the presentdocument, the phrases “A or B” and “A/B” mean (A), (B), or (A and B).

FIG. 1 illustrates a network 100 in accordance with some embodiments.The network 100 may include an AP 104 communicatively coupled with aplurality of stations (STAs) including, for example, STA A 108, STA B112, STA C 116, and STA D 120. The network 100 may be a wireless localarea network (WLAN) that is compatible with IEEE 802.11 protocols. Insome embodiments, the network 100 may also be referred to as a basicservice set (BSS). In some embodiments, the AP 104 and STAs maycommunicate based on high-efficiency wireless (HEW) protocols definedin, for example, IEEE 802.11ax D4.0, February 2019-IEEE Draft Standardfor Information Technology—Telecommunications and Information ExchangeBetween Systems Local and Metropolitan Area Networks—SpecificRequirements Part 11: Wireless LAN Medium Access Control (MAC) andPhysical Layer (PHY) Specifications Amendment Enhancements for HighEfficiency WLAN (hereinafter “IEEE 802.11ax”). STAs operating based onhigh-efficiency (HEW) protocols may also be referred to as HEW orhigh-efficiency (HE) STAs.

In some embodiments, the AP 104 may generate transmissions to theplurality of the STAs of the network by multiplexing the transmissionsin a frequency domain. The AP 104 may include the transmissions tomultiple users in a multiuser packet, for example, a MUhigh-efficiency—physical layer convergence procedure protocol data unit(HE-PPDU), that is transmitted in a downlink transmission.

As briefly described above, multiuser/single user (SU) beamformingrelies on channel knowledge used to select weight vectors of abeamforming matrix. This channel knowledge may be acquired explicitly,for example, a receiver may measure a channel and send channelinformation back to the transmitter. The wireless channel may changeover a short period of time and as the channel knowledge ages, itbecomes less relevant. Reliance on the older channel knowledge maydegrade throughput. The degradation of throughput may be especiallyevident in multiuser scenarios where outdated channel knowledge can leadto a substantial increase in mutual interference detected by thestations. However, requiring frequent channel feedback may imposesignificant overhead. Embodiments of the present disclosure improveperformance by tracking changes in a channel without relying onsubstantial channel feedback overhead.

Some embodiments provide for implicit channel tracking for simultaneousmultiuser transmissions. Embodiments may use differential measurementsbetween successive transmissions in order to track changes in a channel(including interferences) and may adapt transmission/receptionparameters accordingly. The transmitter may implicitly update channelinformation using original channel knowledge together with informationgleaned from transmissions coming back from a receiver without the needto recalibrate the transmitter or receiver.

In some embodiments, the transmitter may use channel reciprocity and mayestimate channel changes from a transmission returning from the receivertogether with the original channel knowledge. The return transmissionsmay include, but are not limited to, multiuser uplink acknowledgmentinformation, multiuser uplink data, etc. The transmitter may use thedifferential channel estimates to modify transmission/receptionparameters (for example, coding rate, transmit power allocations,beamforming matrices, etc.) for subsequent transmissions.

The AP 104 may use channel information obtained from a soundingoperation to precisely determine a first beamforming matrix to be usedto transmit a first MU packet to STAs A-D while they are in a firstlocation. The STAs A-D may move to different locations (shown by dashedlines) and the AP 104 may use subsequent uplink transmissions from theSTAs A-D in their new locations to implicitly update the channelinformation. The AP 104 may then use the updated channel information todetermine an updated second beamforming matrix, which may then be usedto transmit a second MU packet to the STAs A-D while they are in asecond location. This may be done without relying on additional soundingoperations (either in the UL or the DL) and may also be done withoutrecalibrating the receiver.

While movement of the STAs A-D may be one cause for a channel to change,a channel may change for a number of other reasons as well. Embodimentsof the present disclosure apply equally well regardless of a reason whya channel changes.

FIG. 2 illustrates a transmission diagram 200 in accordance with someembodiments. The transmission diagram 200 may describe messages andoperations performed by AP 104 and stations 204. The stations 204 mayinclude stations similar to, and substantially interchangeable with, theSTAs A-D of FIG. 1.

In some embodiments, the AP 204 may perform a sounding operation 208 toacquire a downlink channel for a transmission opportunity (TXOP) period.To perform the sounding operation 208, the AP 104 may transmit a nulldata packet announcement (NDPA) 212 and, subsequently, a null datapacket (NDP) to the stations 204. The stations 204 may measure the NDPand generate feedback information, which is transmitted to the AP 204 inMU beamforming reports 220. In various embodiments, the feedbackinformation may include channel metrics such as an indication of weightvectors to use in a beamforming matrix and signal-to-noise ratios (SNRs)for different subcarriers. Subcarriers may also be referred to as“tones.”

The AP 104 may determine a first beamforming (BF_1) matrix based on thefeedback information. In some embodiments, AP 104 may also determine anumber of other transmission parameters relevant to downlink multiusertransmissions. These other transmission parameters may include, forexample, users/stations within a MU OFDMA group, resource unit (RU)allocations, modulation and coding schemes (MCSs), and transmit powerallocations.

At 228, the AP 104 may also determine reference channel values based onthe MU beamforming reports 220. The determination of the referencechannel values may be performed by the receive chain decoding preamblesof the MU beamforming reports 220. These reference channel values mayprovide information of a state of an uplink channel over which the MUbeamforming reports 220 are transmitted.

At 232, the AP 104 may correlate the reference channel values with theBF_1 matrix. While the BF_1 matrix is generated based on a state of adownlink channel over which the NDPA/NDP messages were transmitted, thetemporal proximity of the NDP/beamforming reports may be sufficient toassume reciprocity between the uplink and downlink channels and,therefore, support the correlation of the reference channel values withthe BF_1 matrix.

The AP 104 may construct a MU packet based on the determinedtransmission parameters and may transmit the MU packet in a downlinktransmission with the BF_1 matrix 236.

The STAs 204 may transmit uplink transmissions at 240. These uplinktransmissions may include acknowledgment information corresponding todata transmitted in the MU packet at 236. Additionally or alternatively,the uplink transmissions may include uplink data.

At 244, the AP 104 may determine updated channel values and calculate asecond beamforming (BF_2) matrix. The updated channel values may beperformed by the receive chain decoding preambles of the uplinktransmissions transmitted at 240 and may provide information withrespect to a state of an uplink channel at a time in which the ULtransmissions are sent at 240. The AP 104 may infer a change in thechannel values between the reference channel values and the updatedchannel values may correspond to a respective change in the beamformingmatrices. Therefore, the BF_2 matrix may be calculated based on the BF_1matrix and a relative change between the updated channel values and thereference channel values.

The AP 104 may construct a second multiuser packet and transmit thesecond multiuser packet in a downlink transmission with the BF_2 matrixat 248. In some embodiments, the construction of the second multiuserpacket may be performed with many of the transmission parametersdetermined based on the sounding operation 208 including, but notlimited to, users/stations within a MU OFDMA group, resource unit (RU)allocations, MCSs, and transmit power allocations. However, in someembodiments one or more of these parameters may also be updated based ona relative change between the updated channel values and the referencechannel values.

The implicit channel updating as described herein may enable atransmitter to transmit for a longer duration. For example, atransmission opportunity duration may be extended for a specific set ofstations. This may be done without the need to explicitly acquire thechannel again, for example, by asking users to resend channelinformation. Embodiments may improve throughput by reducing protocolcomplexity and overhead; increase downlink (DL)/uplink (UL) MU-MIMOthroughput; or increase accuracy of rate tracking with a faster responseto channel changes.

The description of transmission diagram 200 is based on an assumptionthat the AP is performing the implicit channel tracking. However, otherembodiments may include a station performing the implicit channeltracking. In such embodiments, the sounding operation may be an uplinksounding operation and the uplink/downlink portions may be reversed. Forexample, instead of a changes in a DL channel being implicitly trackedbased on changes in an UL channel, changes in an UL channel may beimplicitly tracked based on changes in a DL channel.

FIG. 3A illustrates a multiuser packet 300 that may be generated by theAP 104 and transmitted in a downlink transmission as described in, forexample, transmissions at 228 or 248 of FIG. 2.

The multiuser packet 300 may be referred to as a MU HE-PPDU in someembodiments. The multiuser packet 300 may include a legacy preamble 304,a high-efficiency (HE) preamble 308, and a data portion 312. The legacypreamble 304 and the HE preamble 308 may span a channel bandwidth. Thechannel bandwidth may be 20 megahertz (MHz), 40 MHz, 80 MHz, 80+80 MHz,or 160 MHz in some embodiments.

The legacy preamble 304 may be used for backward compatibility and maybe decodable by legacy stations. The legacy preamble 304 may includetraining fields, for example, legacy—short training field (L-STF) andlegacy—long training field (L-LTF), to synchronize transmitter andreceiver. The legacy preamble 304 may further include a legacy—signalfield (L-SIG) to allow a receiving station to determine a transmissiontime of the multiuser packet. In some embodiments, the L-SIG field mayhave a length that indicates that the packet is a HE packet with a MUpreamble.

The HE preamble 308 may include a repeated legacy—signal field (RL-SIG)316, a HE signal—A field (HE-SIG-A) 320, HE signal-B field (HE-SIG-B)324, and one or more training fields, for example, HE-STF 328 or HE-LTF332.

The RL-SIG 316 may facilitate detection by providing repetition/L-SIGvalidity checks.

The HE-SIG-A 320 may include common transmission parameters for theusers having data within the data portion 312 of the multiuser packet300. In some embodiments, the HE-SIG-A 320 may provide informationregarding MCSs, bandwidth, number of spatial streams, and otherparameter information to allow a receiver to correctly decode themultiuser packet 300. The HE-SIG-A 320 may provide information regardinga network color, remaining TxOP duration, whether the frame is UL or DL,etc.

The HE-SIG-B field may include RU allocation information and per-usersignaling parameters for the users having data within the data portion314. The per-user signaling parameters may include MCSs, number ofstreams, etc. for each resource unit.

The HE-STF 328 and HE-LTF 332 may be used for tuning thetransmitter/receiver for MIMO transmissions. The HE-STF 328 may be usedto improve automatic gain control estimation in a MIMO transmission, andthe HE-LTF 332 may allow a receiver to estimate the MIMO channel betweena set of constellation mapper outputs and the receive chains.

The data portion 312 may include RUs assigned to stations of the OFDMAgroup. In this embodiment, the OFDMA group determined by the AP 104 mayinclude STAs A-D of FIG. 1 with each station being assigned a respectiveRU. For example, STA A 108 may be assigned RU_A 336, STA B 112 may beassigned RU_B 340, STA C 116 may be assigned RU_C 344, and STA D 120 maybe assigned RU_D 348.

FIG. 3B illustrates a packet 352 that may be generated by a station andtransmitted in an uplink transmission as described in, for example,transmissions at 232 or 240 of FIG. 2.

The packet 352 may include a legacy preamble 356, a HE preamble 360, anda data portion 364. The HE preamble 360 may include an RL-SIG 368,HE-SIG A 372, HE-STF 376, and HE-LTF 380. In general, the fields withinthe packet 352 may be similar to the like-named fields described withrespect to multiuser packet 300. The data portion 364 may includeacknowledgment information or uplink data.

In some embodiments, a receiver of the AP 104 may use the HE-LTF 380 asthe basis for determining reference channel values at 228 and theupdated channel values at 244.

FIG. 4 illustrates signal processing circuitry 400 in accordance withsome embodiments. The signal processing circuitry 400 may be included inthe AP 104 or a station in accordance with some embodiments.

The signal processing circuitry 400 may include a control circuitry 404that includes processor/memory circuitry to execute elements of aprotocol stack including, for example, physical (PHY) and media accesscontrol (MAC) layer functionality. The control circuitry 404 may becoupled with receive circuitry 408 and transmit circuitry 412

As used herein, the term “circuitry” may refer to, be part of, orinclude hardware components such as an electronic circuit, a logiccircuit, a processor (shared, dedicated, or group) and/or memory(shared, dedicated, or group), an Application Specific IntegratedCircuit (ASIC), a field-programmable device (FPD) (e.g., afield-programmable gate array (FPGA), a programmable logic device (PLD),a complex PLD (CPLD), a high-capacity PLD (HCPLD), a structured ASIC, ora programmable SoC), digital signal processors (DSPs), etc., that areconfigured to provide the described functionality. In some embodiments,the circuitry may execute one or more software or firmware programs toprovide at least some of the described functionality. In addition, theterm “circuitry” may also refer to a combination of one or more hardwareelements (or a combination of circuits used in an electrical orelectronic system) with the program code used to carry out thefunctionality of that program code. In these embodiments, thecombination of hardware elements and program code may be referred to asa particular type of circuitry.

The receive circuitry 408 may include analog/digital components designedto extract control/data from signals received by the signal processingcircuitry 400. The components may include, but are not limited to,decoders, demodulators, filters, low-noise amplifiers (LNA), switches,receive beamforming circuitry, processing circuitry, etc.

The receive circuitry 408 may be coupled with a receive controller 422of the control circuitry 404. The receive controller 422 may include afeedback/channel analyzer 418 and memory 424 to store receive parameters426. In some embodiments, the receive circuitry 408 and the receivecontroller 422 may be collectively referred to as “receiver.”

The receive parameters 426 may configure the components of the receivecircuitry 408 to be in a first receive state for receiving signals. Forexample, the receive parameters 426 may set a gain of a low-noiseamplifier (LNA), provide a receive-beamforming matrix for beamformingcomponents of the receive circuitry 408, etc.

The feedback/channel analyzer 418 may extract feedback information fromreceived signals from the receive circuitry 408. For example, thesignals received by the feedback/channel analyzer 418 may be beamformingreports, for example, MU beamforming reports 220, which may includefeedback information that includes information relevant to a state of achannel over which corresponding sounding signals were transmitted.

The feedback/channel analyzer 418 may provide feedback information to atransmit controller 430. The transmit controller 430 may determine andstore transmit parameters 434 in memory 436. The transmit parameters 434may be used to configure transmit circuitry 412 for transmission of asignal. In some embodiments, the transmit parameters 434 may includeusers/stations within a MU OFDMA group, RU allocations, MCSs, transmitpower allocations, and beamforming matrices.

The transmit controller 430 may include a digital beamforming block(DBF) 438 that employs digital signal processing algorithms to processchannel information and compute a beamforming matrix that is stored inthe transmit parameters 434. The channel information may includeexplicit channel information (for example, information about a channelacquired through a sounding operation) or implicit channel information(for example, information about a change in channel values correspondingto reciprocal channel). The beamforming matrix may be provided tobeamforming components in the transmit circuitry 412. The beamformingcomponents may apply the beamforming matrix to a transmitted signal toimprove reception at designated receivers. This may be achieved bycombining elements in a phased antenna array in a manner to exploitconstructive and destructive signal interference experienced by thereceivers.

In addition to the beamforming components, the transmit circuitry 412may include additional analog/digital components (for example, encoders,modulators, mappers, filters, power amplifiers, switches, processingcircuitry, etc.) to generate and transmit the signals. In someembodiments, the transmit circuitry 412 and the transmit controller 430may be collectively referred to as “transmitter.”

The feedback/channel analyzer 418 may additionally/alternativelydetermine channel values that indicate a state of a channel over whichsignals are received by an AP/STA that implements the signal processingcircuitry 400. The signals may include, for example, the MU beamformingreports 220 or the UL transmission 240. In some embodiments, thefeedback/channel analyzer 418 may decode a preamble of the receivedsignals (for example, an HE-LTF field of an uplink packet) to determinethe channel values, which may include reference channel values orupdated channel values as described herein.

The receive controller 422 may provide a tracking manager 442 with thechannel values determined by the feedback/channel analyzer 418. Thetracking manager 442 may include an implicit channel difference analyzer(ICDA) 446. The ICDA 446 may compare updated channel values to referencechannel values to determine a change in a state of the channel. The ICDA446 may provide an indication of the change in the channel state to thetransmit controller 430 as channel information. The DBF 438 may thenupdate the beamforming matrix within the transmit parameters 434 toreflect an estimate of the changed channel.

FIG. 5 illustrates an operation flow/algorithmic structure 500 inaccordance with some embodiments. The operation flow/algorithmicstructure 500 may be implemented by an access point, for example, accesspoint 104 or components thereof, for example, signal processingcircuitry 400. In some embodiments, the operation flow/algorithmicstructure 500 may be modified to be performed by a STA or componentsthereof.

At 504, the operation flow/algorithmic structure 504 may includecalculating BF_1 matrix based on feedback information. The feedbackinformation may be obtained upon acquisition of a channel. For example,the feedback information may include beamforming vectors and SNRstransmitted by STAs A-D in the MU beamforming reports 220.

At 508, the operation flow/algorithmic structure 500 may further includetransmitting a first multiuser packet using BF_1 matrix. In someembodiments, the transmitting of the first multiuser packet using theBF_1 matrix may include a DBF controlling beamforming components in atransmit chain to provide a directional transmission to stations havingdata in the first multiuser packet.

At 512, the operation flow/algorithmic structure 500 may further includereceiving uplink transmissions. A receiver of an access point mayreceive and process the uplink transmissions as described herein. Theuplink transmissions received at 512 may include first uplinktransmissions that may serve as a basis for determining referencechannel values. In some embodiments, a receiver may determine thereference channel values by decoding/measuring preambles of the firstuplink transmissions. The first uplink transmissions may betransmissions sent during a sounding operation (for example, MUbeamforming reports 220) or other UL transmissions including, forexample, data or acknowledgment information. The reference channelvalues may correspond to a first state of an uplink channel over whichthe first uplink transmissions are transmitted.

The uplink transmissions received at 512 may further include seconduplink transmissions, which may be received after a period of time haselapsed since receipt of the first uplink transmissions. The seconduplink transmissions may serve as a basis for determining updatedchannel values. The receiver may determine the updated channel values ina manner similar to that described above with respect to the referencechannel values. The second uplink transmissions may include data oracknowledgment information. The updated channel values may correspond toa second state of the uplink channel over which the second uplinktransmissions are transmitted.

At 516, the operation flow/algorithmic structure 500 may further includecalculating BF_2 matrix based on the uplink transmissions. Thecalculation of the BF_2 matrix may be based on a change in the channelvalues determined from receiving of the uplink transmissions at 512. Inparticular, the access point may infer that a change in an uplinkchannel (determined by comparing the updated channel values to thereference channel values) may correspond to a similar change in thedownlink channel. The access point may then use this change in thedownlink channel as a basis for updating the beamforming matrix from theBF_1 matrix to the BF_2 matrix.

At 520, the operation flow/algorithmic structure 500 may further includetransmitting the second multiuser packet using BF_2 matrix. In someembodiments, the transmitting of the second multiuser packet using theBF_2 matrix may include the DBF controlling beamforming components inthe transmit chain to provide a directional transmission to stationshaving data in the second multiuser packet.

FIG. 6 illustrates an operation flow/algorithmic structure 600 inaccordance with some embodiments. The operation flow/algorithmicstructure 600 may be implemented by an access point, for example, accesspoint 104 or components thereof, for example, signal processingcircuitry 400. In some embodiments, the operation flow/algorithmicstructure 600 may be modified to be performed by a STA or componentsthereof.

At 604, the operation flow/algorithmic structure 604 may include storingfirst channel information in memory. In some embodiments, the firstchannel information may include channel metrics obtained from thefeedback information transmitted during a sounding operation used toacquire a downlink channel for a transmission opportunity. In someembodiments, the first channel information may include weight vectors,SNR information, etc.

At 608, the operation flow/algorithmic structure 600 may further includetransmitting a first multiuser packet based on the first channelinformation. In some embodiments, the first channel information may beused as a basis for determining first transmission parameters, includinga first beamforming matrix, coding rate, etc. The transmission of thefirst multiuser packet may then be accomplished using the firsttransmission parameters.

At 612, the operation flow/algorithmic structure 600 may further includereceiving uplink transmissions. The uplink transmissions may includefirst uplink transmissions and second uplink transmissions fromstations, including stations to which the first multiuser packet wassent. In some embodiments, receiving the uplink transmissions may beperformed by setting components of the receive chain to be in a firstreceive state to receive both the first and second uplink transmissions.For example, the receive controller 422 may set receive parameters 426to be the same while the access point receives the first and seconduplink transmissions. Thus, the receiver may not be recalibrated betweenreceipt of the uplink transmissions.

At 616, the operation flow/algorithmic structure 600 may further includestoring second channel information in memory. In some embodiments, thesecond channel information may be determined based on the uplinktransmissions.

The second channel information may be determined by the access pointimplicitly tracking a downlink channel based on an uplink channel statechange. The uplink channel state change may be determined based on thefirst/second uplink transmissions. For example, the access point maydetermine a first UL channel state based on the first uplinktransmissions and determine a second UL channel state based on thesecond uplink transmissions. The access point may then determine anuplink channel state change based on the first and second UL channelstates. The access point may infer reciprocity between the first UL andDL channel states and may also further infer reciprocity between secondUL and DL channel states. Thus, the access point may infer a DL channelstate change similar to the UL channel state change. The access pointmay then determine the second channel information based on the DLchannel state change and the first channel information.

At 620, the operation flow/algorithmic structure 600 may further includetransmitting the second multiuser packet based on the second channelinformation. In some embodiments, the second channel information may beused as a basis for determining second transmission parameters includinga second beamforming matrix, coding rate, etc. The transmission of thesecond multiuser packet may then be accomplished using the secondtransmission parameters.

FIG. 7 illustrates an operation flow/algorithmic structure 700 inaccordance with some embodiments. The operation flow/algorithmicstructure 700 may be implemented by an access point, for example, accesspoint 104 or components thereof, for example, signal processingcircuitry 400. In some embodiments, the operation flow/algorithmicstructure 700 may be modified to be performed by a STA or componentsthereof.

At 704, the operation flow/algorithmic structure 704 may includeacquiring a downlink channel. The acquisition of the downlink channelmay be accomplished by performing a sounding operation. The soundingoperation may include transmitting NPD packets and receiving feedbackinformation in MU beamforming reports. The feedback information mayinclude information from stations based on their receipt of the NPDpackets. This information may provide an indication of a first DLchannel state.

At 708, the operation flow/algorithmic structure 700 may further includedetermining a BF_1 matrix based on the first DL channel state. In someembodiments, the information received from the stations during thesounding operation may include weight vectors that may form the BF_1matrix.

At 712, the operation flow/algorithmic structure 700 may further includegenerating and transmitting a first MU packet using the BF_1 matrix. Insome embodiments, the transmitting of the first MU packet using the BF_1matrix may include a DBF controlling beamforming components in atransmit chain to provide a directional transmission to stations havingdata in the first MU packet.

At 716, the operation flow/algorithmic structure 700 may further includedetermining a change in an uplink channel and a second downlink channelstate. In some embodiments, the change in the uplink channel may bedetermined based on reception of a plurality of uplink transmissionsfrom stations in a network. First uplink transmissions from the stationsmay be measured by the receiver in the access point to establish areference channel state. The access point may receive the first uplinktransmissions as part of, or after, the sounding operation. Seconduplink transmissions from the stations may be measured by the receiverin the access point to establish an updated channel state. The change inthe uplink channel may be determined by comparing the updated channelstate to the reference channel state.

Upon determining the change in the uplink channel, the access point maydetermine the second downlink channel state by inferring a correspondingchange in the downlink channel with reference to the first DL channelstate.

At 720, the operation flow/algorithmic structure 700 may further includedetermining a BF_2 matrix based on the second DL channel state. In someembodiments, the BF_2 matrix may be generated with weight vectors bettersuited to the second DL channel state.

At 724, the operation flow/algorithmic structure 700 may further includegenerating and transmitting a second multiuser packet using the BF_2matrix. In some embodiments, the transmitting of the second MU packetusing the BF_2 matrix may include a DBF controlling beamformingcomponents in a transmit chain to provide a directional transmission tostations having data in the second MU packet. In this manner, the accesspoint may change the direction of the transmission beams to moreaccurately target stations that may have moved since the soundingoperation occurred.

FIG. 8 illustrates an example of a device 800 in accordance with variousembodiments. The device 800 may be an AP, for example, AP 104, or a STA,for example, one of STAs A-D of FIG. 1. The device 800 may include oneor more of application circuitry 805, baseband circuitry 810, one ormore radio front end modules 815, memory circuitry 820, power managementintegrated circuitry (PMIC) 825, and network controller circuitry 835.

The terms “application circuitry” and/or “baseband circuitry” may beconsidered synonymous to, and may be referred to as, “processorcircuitry.” As used herein, the term “processor circuitry” may refer to,is part of, or includes circuitry capable of sequentially andautomatically carrying out a sequence of arithmetic or logicaloperations, or recording, storing, and/or transferring digital data. Theterm “processor circuitry” may refer to one or more applicationprocessors, one or more baseband processors, a physical centralprocessing unit (CPU), a single-core processor, a dual-core processor, atriple-core processor, a quad-core processor, and/or any other devicecapable of executing or otherwise operating computer-executableinstructions, such as program code, software modules, and/or functionalprocesses.

Application circuitry 805 may include one or more central processingunit (CPU) cores and one or more of cache memory, low drop-out voltageregulators (LDOs), interrupt controllers, serial interfaces such as SPI,I2C or universal programmable serial interface module, real time clock(RTC), timer-counters including interval and watchdog timers, generalpurpose input/output (I/O or IO), memory card controllers such as SecureDigital (SD) MultiMediaCard (MMC) or similar, Universal Serial Bus (USB)interfaces, Mobile Industry Processor Interface (MIPI) interfaces andJoint Test Access Group (JTAG) test access ports. As examples, theapplication circuitry 805 may include one or more Intel Pentium®, Core®,or Xeon® processor(s); Advanced Micro Devices (AMD) Ryzen® processor(s),Accelerated Processing Units (APUs), or Epyc® processors; and/or thelike. In some embodiments, the AP 84 may not utilize applicationcircuitry 805, and instead may include a special-purposeprocessor/controller to process IP data received from network core, forexample.

Additionally or alternatively, application circuitry 805 may includecircuitry such as, but not limited to, one or more a field-programmabledevices (FPDs) such as field-programmable gate arrays (FPGAs) and thelike; programmable logic devices (PLDs) such as complex PLDs (CPLDs),high-capacity PLDs (HCPLDs), and the like; ASICs such as structuredASICs and the like; programmable SoCs (PSoCs); and the like. In suchembodiments, the circuitry of application circuitry 805 may compriselogic blocks or logic fabric, and other interconnected resources thatmay be programmed to perform various functions, such as the procedures,methods, functions, etc. of the various embodiments discussed herein. Insuch embodiments, the circuitry of application circuitry 805 may includememory cells (e.g., erasable programmable read-only memory (EPROM),electrically erasable programmable read-only memory (EEPROM), flashmemory, static memory (e.g., static random access memory (SRAM),anti-fuses, etc.)) used to store logic blocks, logic fabric, data, etc.in look-up-tables (LUTs) and the like.

The baseband circuitry 810 may be implemented, for example, as asolder-down substrate including one or more integrated circuits, asingle packaged integrated circuit soldered to a main circuit board or amulti-chip module containing two or more integrated circuits. Althoughnot shown, baseband circuitry 810 may comprise one or more digitalbaseband systems, which may be coupled via an interconnect subsystem toa CPU subsystem, an audio subsystem, and an interface subsystem. Thedigital baseband subsystems may also be coupled to a digital basebandinterface and a mixed-signal baseband subsystem via another interconnectsubsystem. Each of the interconnect subsystems may include a bus system,point-to-point connections, network-on-chip (NOC) structures, and/orsome other suitable bus or interconnect technology, such as thosediscussed herein. The audio subsystem may include digital signalprocessing circuitry, buffer memory, program memory, speech processingaccelerator circuitry, data converter circuitry such asanalog-to-digital and digital-to-analog converter circuitry, analogcircuitry including one or more of amplifiers and filters, and/or otherlike components. In an aspect of the present disclosure, basebandcircuitry 810 may include protocol processing circuitry (for example,signal processing circuitry 400) with one or more instances of controlcircuitry (not shown) to provide control functions for the digitalbaseband circuitry and/or radio frequency circuitry (e.g., the radiofront end modules 815).

The radio front end modules (RFEM) 815 may include radio frequencyintegrated circuits (RFICs), amplifiers (for example, power amplifiersand low-noise amplifiers), and antenna elements to effectuateover-the-air transmissions. The RFEM 815 may include beamformingcircuitry to increase transmission/reception directivity.

The memory circuitry 820 may include one or more of volatile memoryincluding dynamic random access memory (DRAM) and/or synchronous dynamicrandom access memory (SDRAM), and nonvolatile memory (NVM) includinghigh-speed electrically erasable memory (commonly referred to as Flashmemory), phase change random access memory (PRAM), magnetoresistiverandom access memory (MRAM), etc., and may incorporate thethree-dimensional (3D) cross-point (XPOINT) memories from Intel® andMicron®. Memory circuitry 520 may be implemented as one or more ofsolder down packaged integrated circuits, socketed memory modules andplug-in memory cards.

The PMIC 825 may include voltage regulators, surge protectors, poweralarm detection circuitry, and one or more backup power sources such asa battery or capacitor. The power alarm detection circuitry may detectone or more of brown out (under-voltage) and surge (over-voltage)conditions.

The network controller circuitry 835 may provide connectivity to anetwork using a standard network interface protocol such as Ethernet,Ethernet over GRE Tunnels, Ethernet over Multiprotocol Label Switching(MPLS), or some other suitable protocol. Network connectivity may beprovided to/from the device 800 using a physical connection, which maybe electrical (commonly referred to as a “copper interconnect”),optical, or wireless. The network controller circuitry 835 may includeone or more dedicated processors and/or FPGAs to communicate using oneor more of the aforementioned protocols. In some implementations, thenetwork controller circuitry 835 may include multiple controllers toprovide connectivity to other networks using the same or differentprotocols.

The components shown by FIG. 8 may communicate with one another usinginterface circuitry. As used herein, the term “interface circuitry” mayrefer to, is part of, or includes circuitry providing for the exchangeof information between two or more components or devices. The term“interface circuitry” may refer to one or more hardware interfaces, forexample, buses, input/output (I/O) interfaces, peripheral componentinterfaces, network interface cards, and/or the like. Any suitable bustechnology may be used in various implementations, which may include anynumber of technologies, including industry standard architecture (ISA),extended ISA (EISA), peripheral component interconnect (PCI), peripheralcomponent interconnect extended (PCIx), PCI express (PCIe), or anynumber of other technologies. The bus may be a proprietary bus, forexample, used in a SoC based system. Other bus systems may be included,such as an I2C interface, an SPI interface, point to point interfaces,and a power bus, among others.

FIG. 9 is a block diagram illustrating components, according to someexample embodiments, able to read instructions from a machine-readableor computer-readable medium (e.g., a non-transitory machine-readablestorage medium) and perform any one or more of the methodologiesdiscussed herein. Specifically, FIG. 9 shows a diagrammaticrepresentation of hardware resources 900 including one or moreprocessors (or processor cores) 910, one or more memory/storage devices920, and one or more communication resources 930, each of which may becommunicatively coupled via a bus 940. As used herein, the term“computing resource”, “hardware resource”, etc., may refer to a physicalor virtual device, a physical or virtual component within a computingenvironment, and/or physical or virtual component within a particulardevice, such as computer devices, mechanical devices, memory space,processor/CPU time and/or processor/CPU usage, processor and acceleratorloads, hardware time or usage, electrical power, input/outputoperations, ports or network sockets, channel/link allocation,throughput, memory usage, storage, network, database and applications,and/or the like. For embodiments where node virtualization (e.g., NFV)is utilized, a hypervisor 902 may be executed to provide an executionenvironment for one or more network slices/sub-slices to utilize thehardware resources 900. A “virtualized resource” may refer to compute,storage, and/or network resources provided by virtualizationinfrastructure to an application, device, system, etc.

The processors 910 (e.g., a central processing unit (CPU), a reducedinstruction set computing (RISC) processor, a complex instruction setcomputing (CISC) processor, a graphics processing unit (GPU), a digitalsignal processor (DSP) such as a baseband processor, an applicationspecific integrated circuit (ASIC), a radio-frequency integrated circuit(RFIC), another processor, or any suitable combination thereof) mayinclude, for example, a processor 1012 and a processor 914.

The memory/storage devices 920 may include main memory, disk storage, orany suitable combination thereof. The memory/storage devices 920 mayinclude, but are not limited to any type of volatile or non-volatilememory such as dynamic random access memory (DRAM), static random-accessmemory (SRAM), erasable programmable read-only memory (EPROM),electrically erasable programmable read-only memory (EEPROM), Flashmemory, solid-state storage, etc.

The communication resources 930 may include interconnection or networkinterface components or other suitable devices to communicate with oneor more peripheral devices 904 or one or more databases 906 via anetwork 908. For example, the communication resources 1030 may includewired communication components (e.g., for coupling via a UniversalSerial Bus (USB)), cellular communication components, NFC components,Bluetooth® components (e.g., Bluetooth® Low Energy), Wi-Fi® components,and other communication components. As used herein, the term “networkresource” or “communication resource” may refer to computing resourcesthat are accessible by computer devices via a communications network.The term “system resources” may refer to any kind of shared entities toprovide services, and may include computing and/or network resources.System resources may be considered as a set of coherent functions,network data objects or services, accessible through a server where suchsystem resources reside on a single host or multiple hosts and areclearly identifiable.

Instructions 950 may comprise software, a program, an application, anapplet, an app, or other executable code for causing at least any of theprocessors 910 to perform any one or more of the methodologies discussedherein. For example, the instructions 950 may cause one or more of theprocessors 910 to implicitly track a channel for updating transmissionswithin a transmission opportunity duration as described herein.

The instructions 950 may reside, completely or partially, within atleast one of the processors 910 (e.g., within the processor's cachememory), the memory/storage devices 920, or any suitable combinationthereof. Furthermore, any portion of the instructions 950 may betransferred to the hardware resources 900 from any combination of theperipheral devices 904 or the databases 906. Accordingly, the memory ofprocessors 910, the memory/storage devices 920, the peripheral devices904, and the databases 906 are examples of computer-readable andmachine-readable media.

For one or more embodiments, at least one of the components set forth inone or more of the preceding figures may be configured to perform one ormore operations, techniques, processes, and/or methods as set forth inthe example section below. For example, the baseband circuitry asdescribed above in connection with one or more of the preceding figuresmay be configured to operate in accordance with one or more of theexamples set forth below. For another example, circuitry associated witha UE, base station, network element, etc. as described above inconnection with one or more of the preceding figures may be configuredto operate in accordance with one or more of the examples set forthbelow in the example section.

EXAMPLES

Example 1 includes a method of operating an access point, the methodcomprising: calculating a first beamforming matrix based on feedbackinformation received from a sounding operation; transmitting a firstmultiuser packet using the first beamforming matrix, the first multiuserpacket to include data to be transmitted to a plurality of stations ofan orthogonal frequency division multiple access (OFDMA) group;receiving, from the plurality of stations, uplink transmissions;calculating a second beamforming matrix based on the uplinktransmissions; and transmitting a second multiuser packet using thesecond beamforming matrix.

Example 2 may include the method of example 1 or some other exampleherein, wherein the uplink transmissions include acknowledgmentinformation with respect to data within the first multiuser packet.

Example 3 may include the method of example 1 or some other exampleherein, wherein the method further comprises performing the soundingoperation to acquire a channel for a transmission opportunity duration.

Example 4 may include the method of example 3 or some other exampleherein, wherein said transmitting the second multiuser packet is withinthe transmission opportunity duration.

Example 5 may include the method of example 3 or some other exampleherein, wherein the first beamforming matrix corresponds to a firststate of the channel within a first portion of the transmissionopportunity duration and the second beamforming matrix corresponds to asecond state of the channel within a second portion of the transmissionopportunity duration.

Example 6 may include the method of example 1 or some other exampleherein, wherein the uplink transmissions include first uplinktransmissions and second uplink transmissions, wherein calculating thesecond beamforming matrix comprises: determining reference channelvalues based on the first uplink transmissions; determining updatedchannel values based on the second uplink transmissions; and calculatingthe second beamforming matrix based on the updated channel values.

Example 7 may include the method of example 6 or some other exampleherein, wherein the method further comprises controlling a receive chainto receive both the first and the second uplink transmissions with afirst receive state.

Example 8 may include the method of example 6 or some other exampleherein, further comprising: correlating the reference channel values tothe first beamforming matrix; and calculating the second beamformingmatrix based further on the correlation of the reference channel valuesto the first beamforming matrix.

Example 9 may include the method of example 8 or some other exampleherein, further comprising: calculating the second beamforming matrixbased on an inference that a change from the reference channel values tothe updated channel values corresponds to a change from the firstbeamforming matrix to the second beamforming matrix.

Example 10 may include a method comprising: storing first channelinformation based on feedback from a plurality of stations of a wirelesslocal area network in response to one or more reference signals;transmitting a first multiuser packet to the plurality of stations basedon the first channel information; processing uplink transmissionsreceived from the plurality of stations; storing second channelinformation based on the uplink transmissions; and transmitting a secondmultiuser packet based on the second channel information, wherein thefirst channel information corresponds to a downlink channel within afirst portion of a transmission opportunity and the second channelinformation corresponds to the downlink channel within a second portionof the transmission opportunity.

Example 11 may include the method of example 10 or some other exampleherein, further comprising performing a sounding operation to acquirethe downlink channel for the transmission opportunity.

Example 12 may include the method of example 10 or some other exampleherein, wherein the uplink transmissions includes user uplink data orincludes acknowledgment information with respect to data transmitted inthe first multiuser packet.

Example 13 may include the method of example 10 or some other exampleherein, wherein the uplink transmissions include first uplinktransmissions and second uplink transmissions and the method furthercomprises: determining a first uplink (UL) channel state based on thefirst uplink transmissions; determining a second UL channel state basedon the second uplink transmissions; determining an UL channel statechange based on the first UL channel state and the second UL channelstate; determining a downlink (DL) channel state change based on the ULchannel state change; and determining the second channel informationbased on the DL channel state change.

Example 14 may include the method of example 13 or some other exampleherein, further comprising setting components of a receive chain to bein a first receive state to receive both the first and second uplinktransmissions.

Example 15 may include the method of example 10 or some other exampleherein, further comprising: generating first transmission parametersbased on the first channel information; and generating secondtransmission parameters based on the second channel information.

Example 16 may include the method of example 15 or some other exampleherein, wherein the first transmission parameters includes a firstbeamforming matrix or coding rate and the second transmission parametersincludes a second beamforming matrix or coding rate.

Example 17 may include a method comprising generating application datato be transmitted to a plurality of stations; acquiring a downlinkchannel for a transmission opportunity; determining a first beamformingmatrix based on a first state of the downlink channel as indicated infeedback information in multiuser beamforming reports received duringacquisition of the downlink channel; generating a first multiuser packetto be transmitted using the first beamforming matrix; determining achange in an uplink channel based on a plurality of uplinktransmissions; determining a second state of the downlink channel basedon the change in the uplink channel; determining a second beamformingmatrix based on the second state of the downlink channel; generating asecond multiuser packet to be transmitted using the second beamformingmatrix; and transmitting the first and second multiuser packets withinthe transmission opportunity.

Example 18 may include the method of example 16 or some other exampleherein, wherein the plurality of uplink transmissions include firstuplink transmissions and second uplink transmissions and the methodfurther comprises: determining reference channel values based on thefirst uplink transmissions; determining updated channel values based onthe second uplink transmissions; and determining the change in theuplink channel based on a comparison of the reference channel values tothe updated channel values.

Example 19 may include the method of example 16 or some other exampleherein, further comprising controlling a receive chain of the radiofront end module to receive the first and second uplink transmissionswith a first receive state.

Example 20 may include the method of example 16 or some other exampleherein, further comprising: correlating the reference channel values tothe first beamforming matrix; and calculating the second beamformingmatrix based further on the correlation of the reference channel valuesto the first beamforming matrix.

Example 21 may include the method of example 16 or some other exampleherein, wherein the plurality of uplink transmissions include firstuplink transmissions and second uplink transmissions and the methodfurther comprises: determining reference channel values based on thefirst uplink transmissions; determining an updated reference channelvalues based on the second uplink transmissions; and determining thechange in the uplink channel based on a comparison of the updatedchannel values to the reference channel values.

Example 22 may include the method of example 21 or some other exampleherein, wherein the first uplink transmissions include the multiuserbeamforming reports.

Example 23 may include an apparatus comprising means to perform one ormore elements of a method described in or related to any of examples1-22, or any other method or process described herein.

Example 24 may include one or more non-transitory computer-readablemedia comprising instructions to cause an electronic device, uponexecution of the instructions by one or more processors of theelectronic device, to perform one or more elements of a method describedin or related to any of examples 1-22, or any other method or processdescribed herein.

Example 25 may include an apparatus comprising logic, modules, orcircuitry to perform one or more elements of a method described in orrelated to any of examples 1-22, or any other method or processdescribed herein.

Example 26 may include a method, technique, or process as described inor related to any of examples 1-22, or portions or parts thereof.

Example 27 may include an apparatus comprising: one or more processorsand one or more computer readable media comprising instructions that,when executed by the one or more processors, cause the one or moreprocessors to perform the method, techniques, or process as described inor related to any of examples 1-22, or portions thereof.

Example 28 may include a signal as described in or related to any ofexamples 1-22, or portions or parts thereof.

Example 29 may include a signal in a wireless network as shown anddescribed herein.

Example 30 may include a method of communicating in a wireless networkas shown and described herein.

Example 31 may include a system for providing wireless communication asshown and described herein.

Example 32 may include a device for providing wireless communication asshown and described herein.

Any of the above described examples may be combined with any otherexample (or combination of examples), unless explicitly statedotherwise. The foregoing description of one or more implementationsprovides illustration and description, but is not intended to beexhaustive or to limit the scope of embodiments to the precise formdisclosed. Modifications and variations are possible in light of theabove teachings or may be acquired from practice of various embodiments.

What is claimed is:
 1. One or more non-transitory, computer-readablemedia having instructions that, when executed by one or more processors,cause an access point to: calculate a first beamforming matrix based onfeedback information received from a sounding operation; transmit afirst multiuser packet using the first beamforming matrix, the firstmultiuser packet to include data to be transmitted to a plurality ofstations of an orthogonal frequency division multiple access (OFDMA)group; receive, from the plurality of stations, uplink transmissions;calculate a second beamforming matrix based on the uplink transmissions;and transmit a second multiuser packet using the second beamformingmatrix.
 2. The one or more non-transitory, computer-readable media ofclaim 1, wherein the uplink transmissions include acknowledgmentinformation with respect to data within the first multiuser packet. 3.The one or more non-transitory, computer-readable media of claim 1,wherein the instructions, when executed, further cause the access pointto: perform the sounding operation to acquire a channel for atransmission opportunity duration.
 4. The one or more non-transitory,computer-readable media of claim 3, wherein said transmission of thesecond multiuser packet is within the transmission opportunity duration.5. The one or more non-transitory, computer-readable media of claim 3,wherein the first beamforming matrix corresponds to a first state of thechannel within a first portion of the transmission opportunity durationand the second beamforming matrix corresponds to a second state of thechannel within a second portion of the transmission opportunityduration.
 6. The one or more non-transitory, computer-readable media ofclaim 1, wherein the uplink transmissions include first uplinktransmissions and second uplink transmissions, wherein to calculate thesecond beamforming matrix the access point is to: determine referencechannel values based on the first uplink transmissions; determineupdated channel values based on the second uplink transmissions; andcalculate the second beamforming matrix based on the updated channelvalues.
 7. The one or more non-transitory, computer-readable media ofclaim 6, wherein the instructions when executed, further cause theaccess point to: control a receive chain to receive both the first andthe second uplink transmissions with a first receive state.
 8. The oneor more non-transitory, computer-readable media of claim 6, wherein theinstructions, when executed, further cause the access point to:correlate the reference channel values to the first beamforming matrix;and calculate the second beamforming matrix based further on thecorrelation of the reference channel values to the first beamformingmatrix.
 9. The one or more non-transitory, computer-readable media ofclaim 8, wherein the instructions, when executed, further cause theaccess point to: calculate the second beamforming matrix based on aninference that a change from the reference channel values to the updatedchannel values corresponds to a change from the first beamforming matrixto the second beamforming matrix.
 10. An apparatus comprising: memory;and processing circuitry coupled with the memory, the processingcircuitry to: store, in the memory, first channel information based onfeedback from a plurality of stations of a wireless local area networkin response to one or more reference signals; transmit a first multiuserpacket to the plurality of stations based on the first channelinformation; process uplink transmissions received from the plurality ofstations; store, in the memory, second channel information based on theuplink transmissions; and transmit a second multiuser packet based onthe second channel information, wherein the first channel informationcorresponds to a downlink channel within a first portion of atransmission opportunity and the second channel information correspondsto the downlink channel within a second portion of the transmissionopportunity.
 11. The apparatus of claim 10, wherein the processingcircuitry is further to perform a sounding operation to acquire thedownlink channel for the transmission opportunity.
 12. The apparatus ofclaim 10, wherein the uplink transmissions includes user uplink data orincludes acknowledgment information with respect to data transmitted inthe first multiuser packet.
 13. The apparatus of claim 10, wherein theuplink transmissions include first uplink transmissions and seconduplink transmissions and the processing circuitry is further to:determine a first uplink (UL) channel state based on the first uplinktransmissions; determine a second UL channel state based on the seconduplink transmissions; determine an UL channel state change based on thefirst UL channel state and the second UL channel state; determine adownlink (DL) channel state change based on the UL channel state change;and determine the second channel information based on the DL channelstate change.
 14. The apparatus of claim 13, wherein the processingcircuitry is to set components of a receive chain to be in a firstreceive state to receive both the first and second uplink transmissions.15. The apparatus of claim 10, wherein the processing circuitry isfurther to: generate first transmission parameters based on the firstchannel information; and generate second transmission parameters basedon the second channel information.
 16. The apparatus of claim 15,wherein the first transmission parameters includes a first beamformingmatrix or coding rate and the second transmission parameters includes asecond beamforming matrix or coding rate.
 17. An access point having:application circuitry to generate application data to be transmitted toa plurality of stations; baseband circuitry coupled with the applicationcircuitry to: acquire a downlink channel for a transmission opportunity;determine a first beamforming matrix based on a first state of thedownlink channel as indicated in feedback information in multiuserbeamforming reports received during acquisition of the downlink channel;generate a first multiuser packet to be transmitted using the firstbeamforming matrix; determine a change in an uplink channel based on aplurality of uplink transmissions; determine a second state of thedownlink channel based on the change in the uplink channel; determine asecond beamforming matrix based on the second state of the downlinkchannel; and generate a second multiuser packet to be transmitted usingthe second beamforming matrix; and a radio front end module to transmitthe first and second multiuser packets within the transmissionopportunity.
 18. The access point of claim 16, wherein the plurality ofuplink transmissions include first uplink transmissions and seconduplink transmissions and the baseband circuitry is to: determinereference channel values based on the first uplink transmissions;determine updated channel values based on the second uplinktransmissions; and determine the change in the uplink channel based on acomparison of the reference channel values to the updated channelvalues.
 19. The access point of claim 16, wherein the baseband circuitryis further to control a receive chain of the radio front end module toreceive the first and second uplink transmissions with a first receivestate.
 20. The access point of claim 16, wherein the baseband circuitryis further to: correlate the reference channel values to the firstbeamforming matrix; and calculate the second beamforming matrix basedfurther on the correlation of the reference channel values to the firstbeamforming matrix.
 21. The access point of claim 16, wherein theplurality of uplink transmissions include first uplink transmissions andsecond uplink transmissions and the baseband circuitry is to: determinereference channel values based on the first uplink transmissions;determine an updated reference channel values based on the second uplinktransmissions; and determine the change in the uplink channel based on acomparison of the updated channel values to the reference channelvalues.
 22. The access point of claim 21, wherein the first uplinktransmissions include the multiuser beamforming reports.